The present invention relates to a damper device provided in a clutch for a motor vehicle.
Japanese Patent Application Laid-open 60-136626 discloses a damper device of an electromagnetic clutch in which damper springs are disposed between a driven member and a hub of the clutch in tangential directions of the driven member, respectively. The springs operate to transmit the torque of the driven member to the hub. When the transmitting torque exceeds a predetermined value, stopper pins provided in the driven member are moved in the rotational direction to engage with the hub to transmit the torque. Each stopper pin is secured to the driven member at both ends thereof by staking, and a central part of the pin is engaged with the hub. Accordingly, the stopper pin must be made of soft metal for the staking at both ends thereof. However, the central part must be hardened by carburized quench hardening or induction hardening in order to prevent abrasion and wearing thereof. Further, in order to prevent both end portions from carburizing, an anti-carburizing process must be applied to end portions before the hardening process.
Accordingly, a number of steps are required to manufacture the stopper pin, which causes the cost to increase. Moreover, it is difficult to manufacture stopper pins to have uniform quality.
In a continuously variable belt drive automatic transmission of a motor vehicle having a small number of cylinders which has large peak engine torque, since the range of torque loaded on the damper spring is set to a small value compared with the above mentioned peak engine torque, the load range on the stopper pin becomes large. Accordingly, it is important for the automatic transmission to resolve the above described problems.